Alternating-current electric motor.



W: N. DICKINSON, JR- v ALTERNATING CURRENT ELECTRIC MOTOR. APPLICATION 111.111) JUmr 3,1906;

In yeti tor P 1- b7MZW74flM Arty- Patented Jan. 9; 1912; v

To all whom it may concern:

UNITED. sirA'rEs PATENT orrion WILIQIAM n. mcxrnsonan; or new Yonx, n. Y., nssrenonr OTIS ELEVATOR COMPANY, or JERSEY CITY, NEW anus EY, A CORPORATION NEW JERSEY.

nL'rEnNA'rm'G-cnnnnm nLnc'r-mc Moron.

Be it known that I, WILILIAM N.- Diem:-

' soN, Jr., a citizen of the United States, re-

siding at NewYork city, borough. ofv'B rooklyn, State'of New York, have invented a new and useful Improvement in Alternating- Current Electric Motors, of which the fol-' lowing is a specification.

My invention relates to alternating current motor controlling apparatus and one of its objects is the provision of means for operating alternating current electric brakes in conjunction with motors,wi th minimum consumption of current. v

A further object of the invention is the provision of means brake apparatus for electric motors without its application may be general; 1

6- the brake-releasing materially addingto, the starting current required by the motor.

More particularly it is the object of the present invention to provide an alternating.

current electro-magnet for releasing the brake, an additional electro-magnet for hold ing the brake in .released position, and switch,

apparatus for deenergizlng the releasing electro-magnet and energizing the holding electro-magnet. j Y

Other objects of my invention willappear hereinafter, the novel combinations of elements being pointed out-in the claims,

In the accompanying drawing I have illustrated my invention appliedto an alter-.

nat-ing current electric elevator system, but

I M designates a motor of any desired type, preferably, however, a multiphase induction motor comprising a squirrel cage rotor, or a rotor so wound that it may be suitably connected with an exterior starting device containing sectional resistances. l

E designates the hoisting apparatus to which the car 0 is connected by means of the hoisting cable 7 8 passing over the sheaves 79 and 80.

a 5 designates the rotor shaft on which is mounted the brake pulley or coupling 8, the brake 7 being associated with the latter and connected by means of links and levers to and holding apparatus and also to'the swltch device 12.

One of the objectionable features experienced inadding an electric brake to an alternatin current winding machine or a hoist-- ing evice, has beenthe. excessive current required lo 'the motor.

invention for efiiciently' operating,

Specification of Letters Patent. I Pa,tented Jan. 9, 1912. Application filed my a, 1906. Serial No. 324,539.

required. by the brake at atime practically coincident with that at which the maximum current, "namely, the starting -current, was 0 It is awell known fact that the current required to hold the brake in on position, after the magnetic is but a small fraction of that required to lift or release the brake when, the latter is of the regular type. In othe'r'words, the current required" when the magnetic circuit is closed is but a small fraction of that when the magnetic circuit is open.

circuit ofthe brakemagnet has been closed, I

It is the principal object of the present' I to the starting conditions, that the current required to start the elevator does-'not'egr-A ceed. that required for the moto-r,-save for the small amount 'of-current-required to retain the brake in released posit-ion, with the magnetic circuit of the brake magnet closed.

to so adjust .the brake apparatus I therefore employ the regular type of alternating current'brake magnet 14 and add to the same a second magnet 17 which may be smaller in size and which vis desigmed'only to hold the brake in off position after it has been lifted to such position by the larger magnet 14. To the-coils of the releasing 14 are connected at starting the secondary circuit 29 of the induction motor by means of the leads 32, a portionof the switch 12, and the leads 28. This releasing magmagnet net 14 may be connected-to the secondary circuit or rotor circuit of the motor either directly and as a sole connection across said secondary c'ircuit at starting, or it may be connected in shunt wlth or 1n series withresistance. or reactance, or. even with a condenser. In this instance,however, I have connected the magnet 14:- across the. resistances 30, 35, 36 and 37. Taking, however, the case of a multiphase induction motor, in

which, at starting, this releasing magnet14 is connected in shunt with ohmic resistance across the collector or slip rings of the secondary member or rotor'of the motor, it will be clear that upon the usual conditions, the excess current required to start 'the motor under load will provide more than sufiicientenergy in the secondary circuit to liftnor release the brake. It will be furtherv apparent that, owing to the fact that current from the secondary circuit of the motor is passed through the coils of thebrake magnehthis v I Q I 1,014,210

secondary current will be displaced inphase from the position. most advantageous for'ob tainingmaxlmum torque in the secondary member of the motor. If, however, the

' {9 5 switch 12 is designed to connect the primary circuit 84 of the line to thecoi'ls of thesec- 0nd or' holding magnet 1;? after the latters magnetic circuit has been completed, and arrangement is made to have this switch 210- i tua'ted. either by the upward movement of the brake'or by other means which w'ill provide the proper time. connection, 1t will be clear thatnot only will the current draft from the main circuit not be increased above 15 that required by the motor, save for the small current required to hold. the brake. in ofi' p0sition after it has-been lifted to a that position, but, if in combination with the first switch, a second switch is designed to simultaneously,.or approximately so, disconnect the first brake magnet 14 from the secondary circuit, itwill be equally clear that the'condition of reduced torque, owing to detrimental displacement of phase in the secondary circuit, will'exist only for a moment. Furthermore,.;after the second switch is closed, the motor may exert its full starting torque under the most fatorable conditions for which it has'been designed. -Although any suitable switch 12 may be used in connection with the brake apparatus,

I have herein. shown for the purpose of f illustratioma simpleelectric switch comprising, thfee yertically arrangedand fixed contact carrying; device's. Over the fixed contacts' are adapted to slide the cross bars 23' and 24 which "are connected by the vertical bar 25 The cross bars 23 and 24 carry insulated contacts at their outer'ends which are adapted to cooperate with the fixed cont'acts. "Furthermore the cross bars and 24 together with the verticalconnecting'bar .25, aresecured to the rod 5 so that all of these parts move together.

The uppermost fixedcontacts 42 are,cbn

.nected by the leads 26 to the printary'eircuit 34, and the outer contacts4'Z, of the'cross bar,

23 normally engage said pppermost'ifixed contacts.

contacts are connected by means of the wires .27 to the holding electro-magnet 17. The next lower fixed contacts are connected by the conductors 32 to the releasing electro{ magnet 14. These fixed contacts 44 are normally connected by means of-the outer contacts 49 0f the cross bar 24 to the fixed contacts 45, which are in turn connected by means of the conductors 28 to the secondary 39 or rotor circuit 29 of the motor M.

lowermost fixed contacts 46 are connected bymeans of the wires 31 to the conductors 38 of the starting device beyond the resist ance 30. Besides the starting resistance 30' there may be additional starting resistances The insulated fixed contacts 43, 5 immediately below the uppermost fixed of the switch to fail to operate.

The

35, 36 and 37 to obtain any-degree of refinement of acceleration desired.

I Now when the switch S in the car C is moved onto one of its contacts, say that'designated89, a circuit will be closed through onset the reversing switch magnets 85 or 85, in this instance that. designated 85'. The circuitmay be traced from the lead 0 to the solenoid or magnet. 85, wire 92, contacts 93, 9 5, and bridge piece 50, of the machine limit switch 84, wire 96, contact 89, vlever 90, wire 97, slack cable switch 88, wire 100, to one of the other leads, in this instance that designated 6. Upon the-energization of the reversing switch magnet 85 .the reversing switch R will be closed and the stator circuit 84 will at once receive current and the current induced in the secondary or rotor of the motor will supply current-through the leads, 29 and 28,and

thence through the fixed contacts45, 44, and

the movable contacts 49 to the conductors 32 and thence to the releasing;electrormagnet;,,

14. The latter will quicklyiact on the armature 18 to lift the same together with the rod 1 against the action of the spring 15 and thus release the brake 7 through the med'iiim of the lever 6 which is pivoted-at 21, and the link 19 which is 'connectedbetween the lever 6 and, the lever 10. The lever 1.0 has a fixed pivot at 13 and is connected to the brake .7

collar 9-aga-inst which the stop 11 on the rod '5 abut. As.shown,'the cross bars 23 dand '24 are arranged vertically and will therefore descend by gravity when released, but thismay be otherwise arranged if desired, and a retarding device used in connection therewith so' that they will move downwardly at any predetermined rate of speed. In this instance the inertia and friction of the moiging parts of the switch 12 are relied upon to furnish the small time ele ment desired ,toeaccom'plish the object, and the end 9 of the lever 4 is soaarranged as to strike a shoulder 20 on rod 5 in the etent of its failing to drop promptly on being re leased. This guards ilQfllllSt any tendency \Vhen the current is first supplied to the motor, the resistances 3-), 35, 36 and 37 are all connected to'the secondary circuit, and the electro-magnet 14 is connected in shunt thereto. As soon as the reversing switch R is closed, current is supplied by means of the leads 42 and 41 to the accelerating magnets 1mm, i

so as ,to short-'- circuit the resistances 35,36

' and '37 step 'bystep, and thuspermitlthe speed. The

motor to gradually increase in switch 12 is arranged-to short-circuit the resistance 3Q'before the switches 38, 39 and 40 begin to operate as it is desired to employ] current for the releasing magnet l i onlyfl momentarily.

it should be noted that whenthemagnet 14: is energized andthe armature 1 8 drawn upwardly to efiect the releaseof thebrake and-the switch 12, the frame 22 is also moved e upwardly to bring the armature ;18';into en? 'closed, it requires only a small, :currentto time before the contacts 49 leave the fixed contacts 44. IThis'action of the switch 12 gagement with the holding eleetro-magnct v I As stated 1 heretofore, after the'magnetic circuit of an l7'to close its magnetic circuit;

alternating currentv electronagnet has been maintain; it sufiicient-ly energized so that it may holdthe brake'inreleased position; as

soon as the switch 12is released, the-contacts 47 will connect thefixed. contacts i2, 43,:

substantially at. the same time or a short effects the energizationvof the holding 'magnet 17 and the denergization oif'the releas- "ingmagnet 14, and also the short-circuiting of the resistance-30, asexplainedihereinbeand means for almost simultaneously 'com-* pleting the magneticfland electric circuits of fore.--

The limit switches81 and 82 andthesafety switch 48fin the car are {for the pur'pose of energizing tetripping coil 51 of the mainline switch the latter and the consequent stopping of the L to effectthe opening of motor-hoisting apparatus and car. This, however, is no part of the present invention and is therefore not explainedin detail. It

ishoweverdescribed and claimed in my co-' pendingapplication, Serial No. 321,692, filed June 14, 1906, for an improvement in; safety devices for alternating current hoisting apparatus.

' When the switch'S in the car-is opened,of course the reversing-switchwhichhas been I operated will also be opened and the holding magnet The frame 22 will therefore be released and the spring l5 will apply the braketo stop the motorand the link or collar 9'will strike the stop 11 to'move the rod 5 and the crossbar-s 23 and'24 to their upper positions, as shown in ,the drawings.

Obviously those skilled in the art may Qelectric clrcuit of said hol'ding'el'ecti o-mag 17 will be denergizedlas' the pri -mary,jcircuit 3a and the leadsf26 nolonger receive current. v and appliances parts 7 withoutdeparting from the spirit and scope of my invention as defined by the claims, and I desire therefore not to be limited to the precise construca Having thus fully described my ia'ventida Letters Patent of theUnited States is what I claim and desire to have protected g 1'; The combination with "a motor-{of a, I

brake therefor, electroresponsive' means for releasing the brake, a holdingidevice for mamtaming the brake in released position,

and an automatic switch for'render1ng1et,-

' The combinatronwith a motor, ofbrake g apparatus therefor,"electrorespjonsive means for, releasing said brake apparatus, electro ;magnetic' mechanism-for holding saidbrake;

apparatus in released pos'ition, devices co-" acting, with saidirelea'sing"means to-close" fective sa i-ideholdingdevice'after the brake has been released. w

thejmagnetic circuit of said electromagnetic mechanism' before '-its' elec'tire. curcuit is closed, and switch appliances operated by I said, releasing r'n'e'ans for controlling the "ne'erand said electromagnetic meehanism;

3. The combination with a motor, ofbrake Y apparatus therefor," means independentfof movement of any part of the motor'for lre-- leasingsaldbrake apparatus, ah, alternating current holding electro-magnet, and con-- nections to close. the magneticj'circuit of said tric circuit.

alternating current holding =elcctro-magnet,

said holding, electro-magnet and vacting upon a release of the brake,

net for releasing said brakeapparatus, an-

"holding gnagnetand atterwardjcloseits elem; it The combination with amoton of abraltes therefor, brake-applying mechanism, elec r f. troresponsivemeans'to release the brake, an;

saidjbrake-applying mechanism to effect the, 5.'The'comb'nat1on with an alternating" additional alternating current electro-m'ag net for vholding the' brake apparatus in re leased positoin, and a switch forelosing-the net after its magnetic circuit is'closed.

6; The combination with an alternating current motoiyot brake apparatus therefor,

means'independentvofniovementofthe mo- I I tor for releasing saidfbrake apparatus, an

alternating current. holding electro-magnet,

the electric circuit thereof.-

7. The combination with means'zfor :acting upon said brake-applying 'p'lete he magnetic co-acting with said brake- 'releasing'meansto close the magneticcircuit .ot said electro.-magnetand thereafter close r a motor, of a brake therefor, brake-applying apparatus, 7

.a holding electro-magnet, electroresponsive electrosmagnet, and a switch for controlling I said actuating means and said holding magnet," 1 A 8 The -combination with afmotor, of, a, 

